1. Field of the Invention
The present invention relates to a vehicular power distribution control apparatus and control method and more particularly to a control apparatus and method for controlling driving force to be transmitted from one drive shaft to the other drive shafts.
2. Discussion of Related Arts
Generally, the power distribution control between front and rear wheels for four-wheel drive vehicles or the power distribution control between left and right wheels are performed by variably controlling an engagement force, namely a differential limiting torque, of a hydraulically operated multiple-disc friction clutch and the like. The differential limiting control produces a large change in a vehicle maneuverability, depending upon its control characteristic. Further, in case of the differential limiting control having identical control logics and control constants, the maneuverability of a vehicle also varies according to the aged deterioration of tires or the difference of road conditions.
Japanese Patent Application Laid-open No. Toku-Kai-Hei 8-132914 discloses a technology of a vehicular torque distribution apparatus in which a driver directly establishes a differential limiting torque by manual operation based on the driver's judgment of road and traveling conditions to obtain a discretional torque distribution.
However, in order to realize a vehicle maneuverability as intended by a driver, the differential limiting torque must be properly changed according to road conditions or miscellaneous traveling conditions. Accordingly, it is difficult to coincide the manually inputted differential limiting torque with a proper torque in order to obtain an optimum maneuverability.